there is many ways to do this kind of stuff, this is not the most complicated part to honest:
if you plane to have UI for your player wich will clic on it to customize the character, you may do it llike this:
on an Empty GameObject (or your player or anywhere...) add array list containing the differents parts of your character.
you may create as much as array list as needed and reference them with logic name ref to call them in playmaker.
(Eyes, body, pants, foot, etc..)
you may keep gameObject, textures and many variables in those array lists.
so once created, just make your ui responsive to clic by modifying the int ID to get and set your customisation.
